When connecting to a thermostat to some types of modern residential HVAC systems there are sometimes quite a few wires used. In some cases there can be as many as 16 wires. In designing a sleek thermostat that is visually pleasing when wall mounted in a home, it is desirable that the thermostat is not overly large. Thus, there exists a design problem as to how to connect a large number of HVAC control wires to a relatively small thermostat.
Additionally, in some cases the circuitry required to generate some types of control signals can use a relatively large amount of space on the thermostat. For example, in some systems where a “V” wire is used for variable control of fan speed, a relatively large amount of circuitry may be used within the thermostat to generate the signal.
Furthermore, in some cases when a common wire is not present, certain types of thermostat relays and/or switches make power stealing impractical. In some cases adding a common wire between the HVAC system and the thermostat is a costly endeavor.
It is to be appreciated that although exemplary embodiments are presented herein for the particular context of HVAC system control, there are a wide variety of other resource usage contexts for which the embodiments are readily applicable including, but not limited to, water usage, air usage, the usage of other natural resources, and the usage of other (i.e., non-HVAC-related) forms of energy, as would be apparent to the skilled artisan in view of the present disclosure. Therefore, such application of the embodiments in such other resource usage contexts is not outside the scope of the present teachings.